The basic elements of a door jamb are well known. A header jamb frames the top of the door opening, a hinge jamb to which the door is hung frames one side of the door opening, and a strike jamb frames the other side of the door opening. In the past, door jambs were custom made by carpenters at the construction site. This method was time consuming and thus very expensive. Recently, prefabricated door jamb assemblies were developed. Prefabricated door jambs are less expensive to produce and install because they are mass produced, sometimes prefinished, and are quickly installed. Nevertheless, prefabricated door jambs were normally made to fit only certain standard width door openings. Often, door openings did not match the standard door jamb sizes and it became necessary to have door jambs custom made for these door openings.
More recently, adjustable door jamb assemblies have been developed to fit various widths of doorways. Adjustable door jamb assemblies generally include first and second door jamb pieces which are two halves of a door jamb. The two door jamb pieces are placed adjacent one another about the door opening. The two door jamb pieces are then pushed together to fit the width of the door opening.
It is often difficult to align properly the first and second jamb pieces with respect to one another. The two door jamb pieces must be aligned both vertically and horizontally when installed in the door opening. Prior art adjustable door jamb assemblies are often equipped with "guides" to assist in aligning the two door jamb pieces as they are mounted. The prior art guides are generally tongue-and-groove devices. Tongue-and-groove devices are somewhat effective for aligning the two door jamb pieces in either the vertical direction or the horizontal direction but not in both directions at the same time. Nevertheless, a tongue-and-groove device that restricts movement of the two door jamb pieces in the horizontal direction parallel to the plane of the door opening tends to allow some amount of "play" in the vertical direction. Likewise, a tongue-and-groove device that restricts movement in the vertical direction tends to allow some amount of play in the horizontal direction parallel to the plane of the door opening.
Various tongue-and-groove guides for aligning adjustable door jambs have been proposed. One proposal shows a strap with a rectangular channel attached to one-half of the door jamb and a matching converging tongue attached to the other half of the door frame. During assembly of the two halves of the door jamb, the convergent tongue slides into the rectangular channel in the other half of the door jamb. As the tongue slides into the channel, the door jamb halves cannot move relative to one another in the horizontal direction parallel to the plane of the door opening because the vertical sides of the tongue fit tightly against the vertical sides of the channel. However, because the tongue converges in the direction towards the rectangular channel, the top and bottom edges of the tongue do not fit tightly against the top and bottom edges of the channel unless the tongue is fully inserted into the channel. Therefore, such a tongue-and-groove arrangement allows the halves of the door jamb to move vertically as they are being pushed together. As a result, when the door jamb is assembled about a door frame with a width that does not allow the tongue to be fully inserted into the rectangular channel, the halves of the door frame can be misaligned with respect to one another in the vertical direction.
Another proposed guide for aligning the two halves of a door jamb assembly includes two flat rectangular plates each with an identical V-shaped profile along one edge. One plate is attached to one-half of the door jamb and the other plate is attached to the other half of the door jamb so that the V-shaped profiles of the two plates interlock with one another. The interlocking plates provide a guide that restricts the movement of the two door jamb halves in the horizontal direction parallel to the plane of the door opening as the two halves are pushed together. The inner sides of each V-shaped profile holds the vertical walls of the corresponding plate thereby restricting movement in the horizontal direction. However, because the V-shaped profiles are open, they cannot completely restrict movement of the plates and the door jamb halves to which they are connected in the vertical direction, especially when nails are being hammered through the jamb halves to secure the door jamb to the wall. In addition, the V-shaped profile guides are difficult to operate. In order to push the two halves of the door jamb assembly together, the intricate V-shapd profile of the plate attached to one half of the door jamb has to be aligned with the corresponding edge of the plate attached to the other half of the door jamb. This problem is multiplied when several sets of these guides are attached to one door jamb assembly and must be aligned simultaneously.
Therefore, there is a need for a guide for assembling adjustable door jambs that substantially eliminates play between the door jamb pieces in both the vertical direction and in the horizontal direction parallel to the plane of the door opening, and at the same time is quick and simple to operate.